This invention relates to a thermal image development apparatus and particularly to a reader-printer apparatus such as a microfiche reader-printer apparatus having an in-place thermal development means for formation of a hard copy of the displayed material.
There has been an enormous increase in the volume of records, reports and other documentary information in industrial, educational and other institutions. This has resulted in a significant increase in demand for a documentary storage means which can store a large volume of printed matter in a small and compact storage medium but which can also be made readily available for subsequent recovery and viewing, and if necessary, making a hard copy. Microfilm data processing systems have been developed with such capabilities. Generally, a greatly reduced photographic copy is made of the original printed data to form a microimage, and thereby storing large quantities of data in a small portion of a film. Projecting and enlarging apparatus is then available for viewing the microimages on the film, with various search means provided for rapid location and visual recovery of the stored material from the film. The viewing apparatus preferably includes a reproducing means to permit hard copying of the displayed information upon demand. A particularly satisfactory film storage system uses small film cards identified as "microfiche" film sheets or cards. A microfiche is thus a single sheet of film which may be approximately 3".times.5" in size. Generally, each microfiche is able to store the equivalent of several hundred pages of a normal size book, periodical or report. The microimages on the film are obviously such that the data cannot be read without the aide of an enlarging and projection apparatus. Projection apparatus is available to receive a microfiche with means for aligning and displaying a given portion thereof onto a viewing screen to present the subject matter for convenient viewing. The apparatus as noted above preferably includes a print out system for copying of the projected image. Various electrostatic processing devices which form an integrated part of a reader-printer have been suggested. For example, U.S. Pat. No. 3,877,805 discloses a viewer-copier apparatus with an electrostatic copying and liquid developing system. The apparatus has a cabinet with a front wall viewing screen. A microfiche carrier is adapted to slide into a viewing slot in the lower portion of the cabinet. An image projecting system is provided for projecting of an aligned portion of the microfiche, with a suitable mirror system for redirecting of the light along the necessary path to enlarge the image and present the same in convenient reading display on the viewing screen. The printer unit has a copy sheet transport structure to move paper sheets from a storage portion in the back of the housing to a top exposure portion, located to the back side of the mirror. When an exposure is to be made, a directional mirror is removed such that the image is transmitted directly with the paper sheet which has been moved into appropriate alignment the transmitted. The exposed sheet is then moved through a liquid developer applicator with roller means for removing excess fluid and the final discharge of a liquid developed hard copy. The liquid system is suggested to eliminate certain problems associated with move conventional electrostatic copying systems. Other electrostatic systems of course have been suggested. For example, U.S. Pat. No. 3,922,083 discloses a microfiche viewer-reader in which a paper roll is provided and proper lengths are removed and transfered onto an exposure support, and the exposed paper then passed through an electrostatic developer.
Other developers have also been suggested. For example, U.S. Pat. Nos. 3,899,248 and 4,054,379 disclose corona charging and light exposing with suitable liquid toners and developing medium while U.S. Pat. No. 4,054,379 discloses the use of a liquid developer.
In addition to such developer systems, electrostatic and other generalized copying systems have been developed. For example, a thermal developer particularly useful in association with "dry silver" coated paper has been developed by Minnesota Mining and Manufacturing of Minnesota which is capable of creating an excellant hard copy. Generally, U.S. Pat. No. 3,629,549 discloses a thermal developer for such coated paper. U.S. Pat. Nos. 3,575,580 and 3,311,040 show other similar thermal developers. In such systems, the paper is passed between a roller and a curved heated backing wall to heat the paper to the level necessary to develop the image.
However, thermal development with known technology appears relatively slow, and the available systems have been relatively large and expensive. Such a system has not been widely adapted to a microfiche printer-reader in the retail market.